Adults who routinely get less than six hours of shut-eye a night are four times more likely to suffer a stroke, compared with people getting seven or eight hours, according to a study recently presented at the SLEEP 2012 conference in Boston.

To the surprise of the authors, the risk applied to adults who were at a healthy weight, had no risk factors or history of stroke and no increased risk for sleep apnea or other sleep problems.

“People know how important diet and exercise are in preventing strokes,” lead author Megan Ruiter of the University of Alabama in Birmingham toldUSA Today. “The public is less aware of the impact of insufficient amounts of sleep. Sleep is important — the body is stressed when it doesn’t get the right amount.”

The three-year study followed 5,666 adults aged 45 or older. The participants self-reported their sleep duration and stroke symptoms every six months. The researchers recorded the first stroke symptoms, as well as demographic information, stroke risk factors, depression symptoms and various health behaviors.

In healthy people of normal weight, those who slept less than six hours a night were 4.5 more likely to suffer stroke symptoms than people getting seven or eight hours of sleep. Researchers didn’t find the same elevated risk in overweight or obese people.

“Our thought is that habitually sleeping less than six hours is kind of like a precursor,” Ruiter told MSNBC. “It might kind of lead to some of these stronger and more severe risk factors later on.”

Experts recommend that adults get about seven to nine hours of sleep a night, but according to recent data, about 30% of working American adults are eking by on six hours or less.